1. Field of the Invention
The present invention relates to polishing machines, and more specifically to polishing machines for the mechano-chemical polishing of integrated circuit wafers during manufacturing.
2. Description of Related Art
With conventional polishing machines, the wafer to be polished is sandwiched between a pressing diaphragm of a rotary head that rotates the wafer and the surface of a rotary polishing platen. The polishing is performed by virtue of an abrasive in suspension in a liquid that is made to flow between the wafer and the polishing platen. The polishing head includes a disc that bears the diaphragm on its periphery, and a fluid exerts a pressure on this membrane through the disc in order to press the wafer against the polishing surface in a controlled manner. When abrasives in suspension of the colloid type are used with such a polishing machine, there exists a drawback in that the central part of the wafer is perfectly polished but a region near the peripheral edge of the wafer has a significantly smaller thickness removed.